So I have a prepaid base plan now for $15 and lots of leftover data and minutes boosters. I'm thinking about upgrading to the $55 prepaid base plan but will the leftover data and minute boosters be gone or will it still carry forward into the new plan? Keep in mind this is a PREPAID plan and not a monthly plan.

I would double-check with Koodo first, but this reply from 3 years ago suggests that you would lose credit for the base plan if you switched immediately, since there is no proration on prepaid. The link does not say anything about what (if anything) happens to boosters, though, so I expect they would remain as usual.